While bees and wasps inject venom when they sting, mosquitoes simply bite to feed on your blood. The bumps and itchiness that follow come from an anticoagulant that the mosquito injects to prevent your blood from clotting, which triggers a mild allergic reaction that includes the typical round, red bumps.
A piece of surfaced (sanded smooth) 2×4 lumber actually measures 1½ inches thick and 3½ inches wide. In rough-cut condition, a 2×4 is slightly less than 2 inches thick and approximately 4 inches wide. When wood is milled from a rough to a smooth surface, it loses about ¼-inch from each of its four sides.